JP4257528B2 - Multi-cylinder internal combustion engine - Google Patents

Description

  The present invention relates to a multi-cylinder internal combustion engine, and more particularly to a multi-cylinder internal combustion engine provided with an exhaust gas sensor for determining an air-fuel ratio of exhaust gas in an exhaust system.

A catalyst is provided in an exhaust passage of the internal combustion engine as one of exhaust purification apparatuses that purify exhaust gas discharged from the internal combustion engine. It is necessary to control the air-fuel ratio of the exhaust gas flowing into the catalyst to be close to the stoichiometric range in order to fully demonstrate the performance of the catalyst, and in order to achieve such a purpose, an exhaust gas sensor such as an O ₂ sensor is installed near the catalyst inlet. The air-fuel ratio of the internal combustion engine is controlled based on the exhaust air-fuel ratio determined by the exhaust gas sensor (see, for example, Patent Document 1). In the multi-cylinder internal combustion engine disclosed in Patent Document 1, a catalyst is individually provided on the upstream side from the joining portion of the pair of exhaust passages, and a common exhaust gas sensor is provided in a communication passage that communicates the vicinity of the inlets of both catalysts. Yes.
JP 11-280458 A

  However, when an exhaust gas sensor is provided in the vicinity of the catalyst inlet, there will be a certain amount of exhaust system volume upstream from the exhaust gas sensor, and at least the exhaust delay sensor due to this exhaust system volume is at least equivalent to the exhaust gas sensor. This causes a delay in the determination of the exhaust air / fuel ratio. And since the responsiveness of the air-fuel ratio control is reduced with the delay in determining the exhaust air-fuel ratio, there arises a problem that the purification performance is deteriorated due to the breakthrough of the exhaust gas species to the catalyst. Further, when the air-fuel ratio of the internal combustion engine is controlled according to the exhaust air-fuel ratio determination by the exhaust gas sensor, the air-fuel ratio fluctuation (air-fuel ratio self-excited modulation) inevitably occurs due to the exhaust air-fuel ratio determination delay, and the determination delay If the value is large, the amplitude of the air-fuel ratio fluctuation also increases, and there is a problem that fuel consumption deterioration due to an increase in amplitude toward the rich side and combustion deterioration due to an increase in amplitude toward the lean side are likely to occur.

The exhaust air-fuel ratio determination delay can be improved by, for example, attaching an exhaust gas sensor to the exhaust port of the internal combustion engine and reducing the exhaust system volume upstream of the exhaust gas sensor. Since an exhaust gas sensor is required for each port, another problem arises that the manufacturing cost increases.
It is an object of the present invention to provide a multi-cylinder internal combustion engine that can reduce the manufacturing cost by reducing the required number of exhaust gas sensors and can realize the exhaust air / fuel ratio determination with good responsiveness.

In order to achieve the above object, a first aspect of the invention relates to a multi-cylinder internal combustion engine having a plurality of cylinders, a catalyst for purifying exhaust gas provided in an exhaust passage extending from an exhaust port of each cylinder, and a cylinder of the internal combustion engine. It is built in the flange joint between the head and the exhaust passage, and has an exhaust communication passage communicating at least two exhaust passages and an exhaust gas sensor provided in the exhaust communication passage, and exhausts the distance from the exhaust port to the exhaust gas sensor. This is shorter than the distance from the port to the upstream inlet of the catalyst.

Therefore, the exhaust gas discharged from the exhaust port of each cylinder flows through the exhaust passage, and a part of the exhaust gas is taken into the exhaust communication passage and reaches the exhaust gas sensor. The exhaust gas sensor detects the air-fuel ratio of the exhaust gas of each cylinder. Are detected sequentially.
Since the exhaust gas flowing through at least two exhaust passages is guided to the common exhaust gas sensor through the exhaust communication passage and the air-fuel ratio is detected, the required number of exhaust gas sensors is the number of cylinders of the internal combustion engine (in other words, , When an exhaust gas sensor is provided for each exhaust port). On the other hand, since the distance from the exhaust port to the exhaust gas sensor is shorter than the distance from the exhaust port to the upstream inlet of the catalyst, the transport delay until the exhaust gas discharged from the exhaust port reaches the exhaust gas sensor is minimized. The air-fuel ratio can be detected with good response.
In addition, since the exhaust communication passage is built in the flange joint portion, heat dissipation of the exhaust gas flowing through the exhaust communication passage is suppressed, and the exhaust gas can be supplied to the exhaust gas sensor while maintaining a high temperature.

According to a second aspect of the present invention, in the first aspect, the exhaust communication passage is formed as a groove on at least one of the flange surfaces of the cylinder head side and the exhaust passage side of the internal combustion engine, and is closed when the flange is joined. Function as a passageway .

Therefore, the grooves formed on the flange surface that acts as a path is closed with the flange connection.

  As a preferred aspect, in the multi-cylinder internal combustion engine according to claims 1 and 2, it is desirable that the volumes of the exhaust communication passages from the exhaust passages or the exhaust port side exhaust passages of the respective cylinders to the exhaust gas sensor are set to be substantially equal. If configured in this way, the pressure pulsation when the exhaust gas of each cylinder circulates in the exhaust communication passage is equally affected to perform gas exchange evenly, and accurate exhaust gas that uniformly reflects the air-fuel ratio of each cylinder. The determination of the air-fuel ratio can be realized.

Invention 請 Motomeko 3, in multi-cylinder internal combustion engine having a plurality of cylinders, communicates with a catalyst for purifying exhaust gas provided in an exhaust passage extending, at least two exhaust passages from the exhaust port of each cylinder An exhaust communication path, an exhaust gas sensor provided in the exhaust communication path, an exhaust gas sensor and an intake system of the internal combustion engine communicate with each other, and an intake system that promotes gas exchange in the exhaust communication path by a pressure difference between the exhaust pressure and the intake pressure. The sum of the effective joint areas of the exhaust communication passages relative to the exhaust gas sensor is set larger than the effective cross sectional area of the intake communication passages relative to the exhaust gas sensor .

Therefore, the exhaust gas sensor communicates with the exhaust system (exhaust passage) through the exhaust communication passage, and also communicates with the intake system through the intake communication passage, and the gas in the exhaust communication passage is caused by the pressure difference between the exhaust pressure and the intake pressure. Exchange is facilitated. Further, the amount of exhaust gas flowing through the exhaust gas sensor increases with an increase in the pressure ratio between the exhaust pressure and the intake pressure, and when the pressure ratio reaches the critical ratio and reaches a critical state, the increase in the exhaust gas flow rate is limited. When the cross-sectional area is set as in the present invention, the outlet side of the exhaust gas sensor (the intake communication passage side) reaches a critical state earlier, and the increase in the exhaust gas flow rate is restricted at this point, and this point is used as a boundary. Exhaust pressure acts on the upstream side, and intake pressure acts on the downstream side. Therefore, exhaust pressure close to atmospheric pressure acts on the exhaust gas sensor, reducing the pressure-dependent influence of the exhaust gas sensor, and improving the exhaust air / fuel ratio determination accuracy .
According to a fourth aspect of the present invention, in a multi-cylinder internal combustion engine having a plurality of cylinders, an exhaust gas that is provided in an exhaust passage extending from an exhaust port of each cylinder and purifies exhaust gas, and that communicates at least two or more exhaust passages. An intake communication passage that communicates the communication passage, an exhaust gas sensor provided in the exhaust communication passage, an exhaust gas sensor and an intake system of the internal combustion engine, and promotes gas exchange in the exhaust communication passage by a pressure difference between the exhaust pressure and the intake pressure The sum of the effective cross-sectional area of the exhaust communication passage to the exhaust gas sensor is set smaller than the effective cross-section area of the intake communication passage to the exhaust gas sensor, and the effective connection of each exhaust communication path to the exhaust gas sensor The cross-sectional areas are set substantially equal to each other .
Therefore, the exhaust gas sensor communicates with the exhaust system (exhaust passage) through the exhaust communication passage, and also communicates with the intake system through the intake communication passage, and the gas in the exhaust communication passage is caused by the pressure difference between the exhaust pressure and the intake pressure. Exchange can be promoted. If it is not necessary to take measures against the pressure dependence of the exhaust gas sensor, the exhaust gas sensor inlet side (exhaust communication passage side) will reach a critical state earlier if it is configured as in the present invention. Although the increase in exhaust gas flow rate is limited, the effective cross-sectional area of each exhaust communication passage is substantially equal, so the amount of exhaust gas flowing into the exhaust gas sensor from each exhaust communication passage is not affected by fluctuations in exhaust pressure of each cylinder. It becomes equal, and the accurate determination of the exhaust air-fuel ratio that uniformly reflects the air-fuel ratio of each cylinder is realized .

According to a fifth aspect of the present invention, in the third and fourth aspects, a cooling space is formed downstream of the exhaust gas sensor to promote gas exchange in the exhaust communication path due to a volume change due to cooling of the exhaust gas. so they become the volume substantially the same degree of the exhaust communication passages, the volume of the cooling space, the volume of the exhaust communication passages, a shall have at least one temperature decrease rate is set in the cooling space.
Therefore, the exhaust gas introduced into the cooling space through the exhaust gas sensor changes in volume (volume reduction) due to a temperature drop, and along with this volume change, the exhaust gas upstream from the cooling space is transferred into the cooling space and the exhaust gas is exhausted. The exhaust gas in the communication passage is transferred to the exhaust gas sensor side, and as a result, gas exchange in the exhaust communication passage is further promoted. As the exhaust gas volume changes in the cooling space, almost all of the exhaust gas in the exhaust communication passage is transferred to the intake communication passage and the exhaust downstream communication passage, so that the gas exchange in the exhaust communication passage is efficiently promoted. Is done.

A sixth aspect of the present invention is the method according to any one of the third to fifth aspects, wherein the exhaust communication passages are arranged at substantially equal intervals for each predetermined angle on a substantially horizontal plane with respect to the intake communication passage.
Therefore, since the exhaust communication passages are arranged at substantially equal intervals at predetermined angles on a substantially horizontal plane with respect to the intake communication passage, the exhaust gas in each exhaust communication passage passes through the exhaust gas sensor under substantially the same conditions as the intake communication passage. As a result, the entire circumference of the exhaust gas sensor is utilized for detecting the air-fuel ratio of the exhaust gas, and the responsiveness is improved, and the influence of the air-fuel ratio of the specific cylinder is prevented from becoming stronger or weaker. Accurate exhaust air-fuel ratio determination that uniformly reflects the fuel ratio is realized.

According to a seventh aspect of the invention, according to claim 3-6, the intake communication passage is shall have an adjustable opening and closing valve and the amount of exhaust gas flowing through the intake communication passage.
Therefore, if the opening / closing valve opening is reduced or fully closed in the operating region where there is a possibility of deterioration of combustion, the amount of exhaust gas recirculated to the intake system of the internal combustion engine via the intake communication passage is limited, thereby preventing deterioration of combustion. .

According to an eighth aspect of the present invention, in a multi-cylinder internal combustion engine having a plurality of cylinders, an exhaust gas that is provided in an exhaust passage extending from an exhaust port of each cylinder and purifies exhaust gas, and communicates at least two exhaust passages. A communication passage, an exhaust gas sensor provided in the exhaust communication passage, and the exhaust gas sensor and the exhaust system of the internal combustion engine communicate with the downstream side of the catalyst, and a pressure difference between the upstream side and the downstream side of the exhaust system Are provided with an exhaust downstream communication passage that facilitates gas exchange, and an open / close valve that is provided in the exhaust downstream communication passage and that can adjust the amount of exhaust gas flowing in the exhaust downstream communication passage .
Therefore, at the time of cold start, a phenomenon occurs in which unburned gas due to the increase in fuel is exhausted by bypassing the catalyst through the exhaust downstream communication passage. At this time, if the opening / closing valve opening is reduced or fully closed, the exhaust gas The amount of exhaust gas flowing through the downstream communication passage is limited, and exhaust gas deterioration is prevented.
A ninth aspect of the present invention is that in the eighth aspect , the exhaust communication passages are arranged at substantially equal intervals at predetermined angles on a substantially horizontal plane with respect to the exhaust downstream communication passage.
Accordingly, the exhaust communication passages are arranged at substantially equal intervals at predetermined angles on a substantially horizontal plane with respect to the exhaust downstream communication passage, so that the exhaust gas in each exhaust communication passage is substantially the same as the exhaust downstream communication passage through the exhaust gas sensor. As a result, the entire circumference of the exhaust gas sensor is used for detecting the air-fuel ratio of the exhaust gas, thereby improving the response and preventing the influence of the air-fuel ratio of the specific cylinder from becoming stronger or weaker. This makes it possible to accurately determine the exhaust air-fuel ratio that uniformly reflects the air-fuel ratio.

As described above, according to the multi-cylinder internal combustion engine of the first and second aspects of the invention, the required number of exhaust gas sensors can be reduced to reduce the manufacturing cost, and the exhaust air / fuel ratio can be determined with good responsiveness . In addition, it is possible to suppress the heat release of the exhaust gas and to achieve inactivation prevention and early activation of the exhaust gas sensor .
According to the multi-cylinder internal combustion engine of the third aspect of the invention, gas exchange of the exhaust gas in the exhaust communication passage can be promoted by utilizing the pressure difference between the exhaust pressure and the intake pressure of the internal combustion engine, and the exhaust gas sensor is brought to atmospheric pressure. By applying a close exhaust pressure, it is possible to reduce the pressure-dependent influence of the exhaust gas sensor, and to improve the accuracy of determining the exhaust air / fuel ratio .

According to the multi-cylinder internal combustion engine of the fourth aspect of the invention, the gas exchange of the exhaust gas in the exhaust communication passage can be promoted using the pressure difference between the upstream and downstream of the exhaust system of the internal combustion engine, and the exhaust pressure of each cylinder The exhaust gas amount flowing into the exhaust gas sensor from each exhaust communication passage without being affected by fluctuations can be made substantially equal, and accurate exhaust air / fuel ratio determination can be realized that uniformly reflects the air / fuel ratio of each cylinder .
According to the multi-cylinder internal combustion engine of the fifth aspect of the present invention, in addition to the third and fourth aspects, the exchange of the exhaust gas in the exhaust communication passage can be promoted by utilizing the volume change of the exhaust gas by the cooling space, and the cooling space Since the volume change of the exhaust gas is substantially the same as the volume of the exhaust communication passage, gas exchange in the exhaust communication passage can be promoted efficiently .

According to the multi-cylinder internal combustion engine of the sixth aspect of the invention, in addition to the third to fifth aspects , the exhaust communication passages are arranged at substantially equal intervals at predetermined angles on a substantially horizontal plane with respect to the intake communication passages. In addition to improving the responsiveness of the exhaust gas sensor, it is possible to realize accurate exhaust air / fuel ratio determination that uniformly reflects the air / fuel ratio of each cylinder.
According to the multi-cylinder internal combustion engine of the seventh aspect of the invention, in addition to the third to sixth aspects , in the operation region where there is a risk of deterioration of combustion, the amount of exhaust gas recirculated to the intake system of the internal combustion engine through the intake communication passage is reduced. Combustion deterioration can be prevented by limiting by an open / close valve .

According to the multi-cylinder internal combustion engine of the eighth aspect of the invention, at the time of cold start, the amount of exhaust gas flowing through the exhaust downstream communication passage is limited by the open / close valve, so that the unburned gas due to the increase in fuel bypasses the catalyst. It is possible to prevent the exhaust gas from deteriorating.
According to the multi-cylinder internal combustion engine of the ninth aspect of the invention, in addition to the eighth aspect , the exhaust communication passages are arranged at substantially equal intervals at predetermined angles on a substantially horizontal plane with respect to the exhaust downstream communication passage. The responsiveness of the exhaust gas sensor can be improved, and an accurate determination of the exhaust air / fuel ratio that uniformly reflects the air / fuel ratio of each cylinder can be realized .

[First Embodiment]
Hereinafter, a first embodiment of a multi-cylinder internal combustion engine embodying the present invention will be described.
FIG. 1 is an overall configuration diagram showing a multi-cylinder internal combustion engine of the present embodiment. The internal combustion engine of the present embodiment is configured as an in-line four-cylinder engine. In the figure, the illustration of the engine body is omitted and only the exhaust system is shown. ing. An upstream flange 2 of an exhaust manifold 1 (exhaust passage) is connected to a side surface of a cylinder head of the internal combustion engine by a bolt (not shown) using a surrounding bolt hole 2a, and an exhaust port 10 of each cylinder is connected to the upstream flange 2. The upper portions of the branches 3 (exhaust port side exhaust passages) are welded so as to correspond to each other. The downstream side of the branch 3 of the # 1 and # 4 cylinders and the downstream side of the branch of the # 2 and # 3 cylinders merge with each other to form an exhaust passage merging portion 4, and both exhaust passage merging portions 4 are downstream flanges. 5 is welded.

  A flange 7 of an exhaust pipe 6 (exhaust passage) is connected to the downstream flange 5 of the exhaust manifold 1 by a bolt (not shown), and the upstream side of the exhaust pipe 6 welded to the flange 7 has a bifurcated shape. While communicating with the exhaust passage merging portion 4 respectively, the downstream side of the exhaust pipe 6 is joined to the catalyst 9 after joining at the exhaust passage merging portion 8, and further extends to the rear portion of the vehicle via a silencer (not shown). . Therefore, during operation of the internal combustion engine, exhaust gases discharged from the exhaust ports 10 are sequentially joined while being guided in the exhaust manifold 1 and the exhaust pipe 6, and then discharged to the outside through the catalyst 9 and the silencer.

Each branch 3 of the exhaust manifold 1 is connected to one end of an exhaust communication passage 11 having a pipe shape in the vicinity of the welded portion with respect to the upstream flange 2, and the other end of each exhaust communication passage 11 is gathered at one point. Are connected to the sensor fixing base 12. An exhaust gas sensor 13 is fixed to the sensor fixed base 12, and the exhaust gas sensor 13 and each exhaust communication path 11 communicate with each other inside the sensor fixed base 12. The exhaust gas sensor 13 may be any sensor such as an O ₂ sensor, an air-fuel ratio sensor, a NOx sensor, or the like. Further, the exhaust communication passage 11 may be connected to an exhaust port (not shown) instead of the exhaust manifold 1.

The exhaust gas sensor 13 is electrically connected to an ECU (electronic control unit) mounted on the vehicle, and the output of the exhaust gas sensor 13 is input to the ECU. Based on the exhaust air / fuel ratio determined by the exhaust gas sensor 13, the ECU executes air / fuel ratio control in which a small air / fuel ratio change is required, such as air / fuel ratio control of the internal combustion engine, such as air / fuel ratio feedback control and combustion limit control.
Each exhaust communication passage 11 extends upward from each branch 3, is bent at a substantially right angle, and extends toward the sensor fixing base 12 located between the cylinders # 2 and # 3. The whole is located immediately above the exhaust manifold 1. Because of such a layout, the distance A1 along the exhaust gas flow path from the exhaust port 10 to the exhaust gas sensor 13 (the length of the exhaust communication path 11 differs depending on the cylinder, but is the longer # 1 or # 4 cylinder. Is shortened to the minimum necessary, and is much shorter than the distance A2 from the exhaust port 10 to the upstream inlet of the catalyst 9.

In the multi-cylinder internal combustion engine of the present embodiment configured as described above, the exhaust air / fuel ratio is determined by the exhaust gas sensor 13 as follows.
During operation of the internal combustion engine, exhaust gas is discharged from each exhaust port 10 in accordance with the ignition sequence of # 1-# 3-# 4-# 2 and flows through the branch 3 of the exhaust manifold 1. In the branch 3, a part of the exhaust gas is taken into the exhaust communication passage 11, and mainly reaches the exhaust gas sensor 13 through the exhaust communication passage 11 due to the gas diffusion action, so that the exhaust gas sensor 13 is supplied through the exhaust communication passage 11. The air-fuel ratio of the exhaust gas in each cylinder is detected sequentially. Here, since the distance A1 from the exhaust port 10 to the exhaust gas sensor 13 is very short as described above, the transport delay until the exhaust gas discharged from the exhaust port reaches the exhaust gas sensor 13 is suppressed to a minimum. Compared to a general layout in which the exhaust gas sensor 13 is attached to the upstream side inlet of the catalyst 9, it is possible to realize the exhaust air / fuel ratio determination with very good responsiveness.

  As a result, the responsiveness of the air-fuel ratio control executed by the ECU based on the air-fuel ratio determination is also improved. Therefore, it is possible to prevent the exhaust gas species from passing through the catalyst 9 and prevent the purification performance from deteriorating. In addition, since high-speed self-excited modulation with a small amplitude can be realized by air-fuel ratio control with good response, it is possible to prevent deterioration of fuel consumption due to an increase in amplitude to the rich side and combustion deterioration due to an increase in amplitude to the lean side. As shown in the characteristic diagram of FIG. 2, the efficiency of purifying the crossover point (COP) between THC and NOx can be improved as the modulation period of the air-fuel ratio is shortened.

On the other hand, since the exhaust gas discharged from each cylinder is guided to the common exhaust gas sensor 13 through the exhaust communication passage 11 and the air-fuel ratio is detected, for example, when the exhaust gas sensor 13 is individually installed in the exhaust port 10 of each cylinder As compared with the above, the required number of exhaust gas sensors 13 can be reduced, and consequently the manufacturing cost of the internal combustion engine can be reduced.
Further, as is apparent from FIG. 1, the exhaust communication passages 11 are all connected via the exhaust gas sensor 13 without being in direct communication with each other. According to this configuration, a part of the pressure pulsation generated in the exhaust communication passage 11 is blocked by the exhaust gas sensor 13, so that the exhaust interference of each cylinder is suppressed to prevent the engine output from being reduced due to the exhaust interference. Can do.

  By the way, while high-speed self-excited modulation can improve the COP purification efficiency as described above, the so-called window width tends to be reduced by shortening the modulation period as shown in FIG. Therefore, when the control for actively changing the air-fuel ratio is carried out, or when the air-fuel ratio deviates from the target air-fuel ratio due to some factor, there is a high possibility that the window will be out of the window in the high-speed self-excitation modulation. Therefore, the HC purge may be performed on the catalyst 9 by executing a lean spike every predetermined period or by executing a lean spike after a predetermined rich determination by the exhaust gas sensor 13.

  In order to prevent HC emission when the air-fuel ratio deviates from the window, an appropriate delay time may be set for the air-fuel ratio determination by the exhaust gas sensor 13 to intentionally extend the period of high-speed self-excitation modulation. Even in this case, since the period of high-speed self-excited modulation can be set arbitrarily, the period of self-excited modulation can be increased as much as possible while preventing HC discharge. The responsiveness of the fuel ratio determination can be ensured.

  In this embodiment, the exhaust communication passages 11 of the respective cylinders are gathered at one point and connected to a single exhaust gas sensor 13. However, the exhaust gas sensors 13 having a number smaller than the number of cylinders are provided, and any of the exhaust gas sensors 13 is provided. If it is the structure which connects the exhaust communication path 11 of each cylinder, the layout of the exhaust communication path 11 and the number of the exhaust gas sensors 13 can be variously changed. Therefore, for example, the exhaust communication passage 11 for three cylinders may be connected to the single exhaust gas sensor 13, or the exhaust communication passage 11 for two cylinders may be connected to the single exhaust gas sensor 13.

By the way, in this embodiment, since the transfer of the exhaust gas in the exhaust communication passage 11 is mainly performed by the gas diffusion action as described above, there is a tendency that the exhaust gas is not exchanged smoothly in the exhaust communication passage 11. is there. Accordingly, second to fifth embodiments in which gas exchange promoting means for promoting gas exchange in the exhaust communication passage 11 are added will be described below. The basic configuration (setting of distances A1, A2, etc.) of each embodiment is the same as that of the first embodiment, and the difference is the configuration that promotes the gas exchange. Therefore, the difference is mainly described. And the location of a common structure attaches | subjects the same member number, and the overlapping description is abbreviate | omitted.
[Second Embodiment]
FIG. 3 is a cross-sectional view showing a connection state of the exhaust communication passage 11 to the exhaust manifold 1 of the multi-cylinder internal combustion engine of the present embodiment. In the present embodiment, for the purpose of promoting gas exchange, an inflow portion 21 (gas exchange promoting means) at the tip of the exhaust communication passage 11 is arranged so that the exhaust gas easily flows into the exhaust communication passage 11. That is, the exhaust communication passage 11 of the first embodiment is simply connected to the branch 3 of the exhaust manifold 1 at a right angle, whereas in the present embodiment, the exhaust communication passage 11 is exhausted in a direction to bring the inflow portion 21 closer to the head side. The communication passage 11 is inclined and the inflow portion 21 protrudes into the branch 3 and is positioned near the exhaust valve 22 in the exhaust port 10.

  In the vicinity of the exhaust valve 22 in the exhaust port 10, the exhaust gas from the combustion chamber 23 is discharged obliquely upward along the exhaust gas stream line L1 indicated by an arrow in the figure, but with respect to this exhaust gas stream line L1, The inflow line L2 (in other words, the axial center of the inflow portion 21) when the exhaust gas flows into the inflow portion 21 of the exhaust communication path 11 forms an acute angle α. Therefore, the exhaust gas discharged from the combustion chamber 23 to the exhaust port 10 positively flows into the inflow portion 21 of the exhaust communication passage 11 due to the kinetic energy at the time of discharge, and further reaches the exhaust gas sensor 13 through the exhaust communication passage 11. To do.

As a result, the exhaust gas in each cylinder is smoothly transferred to the exhaust gas sensor 13 through the exhaust communication passage 11 and compared with the first embodiment in which the exhaust gas is transferred mainly by gas diffusion action. Therefore, the responsiveness of the air-fuel ratio determination by the exhaust gas sensor 13 can be further improved as compared with the first embodiment.
The connection state of the exhaust communication passage 11 to the exhaust manifold 1 is not limited to the above embodiment, and may be configured as shown in FIG. 4, for example. In this example, the exhaust communication passage 11 is inclined as described above, and the inflow portion 21 of the exhaust communication passage 11 is opened near the outlet in the exhaust port 10. At the outlet of the exhaust port 10, the exhaust gas flows substantially horizontally along the exhaust gas stream line L1 indicated by an arrow in the figure, but the inflow line L2 to the inflow portion 21 with respect to the exhaust gas stream line L1 has an acute angle α Therefore, the same effect as the above embodiment can be obtained.
[Third Embodiment]
FIG. 5 is a view showing a connection state of the intake communication passage of the multi-cylinder internal combustion engine of the present embodiment. In the present embodiment, for the purpose of promoting gas exchange, the exhaust gas sensor 13 is connected to the intake system of the internal combustion engine to generate a pressure difference before and after the exhaust gas sensor 13. That is, only the exhaust communication passage 11 is connected to the exhaust gas sensor 13 of the first embodiment, whereas in the present embodiment, in addition to the exhaust communication passage 11, one intake communication passage 31 ( One end of the gas exchange promoting means) is connected, and the other end of the intake communication passage 31 is connected to the intake manifold 32. Accordingly, the exhaust gas sensor 13 communicates with the branch 3 of each cylinder of the exhaust manifold 1 through the exhaust communication passage 11, and also communicates with the intake manifold 32 through the intake communication passage 31.

  Exhaust pressure (positive pressure) acts on the branch 3 to which the exhaust communication passage 11 is connected, while intake pressure (negative pressure) is generated in the intake manifold 32 to which the intake communication passage 31 is connected. Therefore, a pressure difference is generated before and after the exhaust gas sensor 13. Therefore, the exhaust gas in the exhaust communication passage 11 flows through the exhaust gas sensor 13 to the low pressure side intake communication passage 31, and as a result, the exhaust gas of each cylinder is smoothly transferred to the exhaust gas sensor 13 through the exhaust communication passage 11. Therefore, gas exchange of the exhaust gas in the exhaust communication passage 11 can be promoted.

By the way, since it is necessary to secure a certain cross-sectional area in the intake communication passage 31 in order to prevent blockage due to the flow of exhaust gas, as a result, more exhaust gas than the amount necessary for promoting gas exchange is taken into the intake communication passage 31 through the intake communication passage 31. There is a tendency to return to the manifold 32 side. Therefore, in the EGR control, when the EGR amount is increased to near the combustion limit in order to reduce NOx, the exhaust gas recirculated through the intake communication passage 31 can cause combustion deterioration. Therefore, as shown by a broken line in FIG. 5, an opening / closing valve 33 is provided in the intake communication passage 31, and the opening degree of the opening / closing valve 33 is reduced or fully closed in the operation region where there is a risk of deterioration of the combustion. The amount of exhaust gas recirculated to the intake manifold 32 side through 31 may be limited to prevent combustion deterioration.
[Fourth Embodiment]
FIG. 6 is a view showing a connection state of the exhaust downstream communication passage of the multi-cylinder internal combustion engine of the present embodiment. In this embodiment, for the purpose of promoting gas exchange, the exhaust gas sensor 13 is connected to the downstream side of the catalyst 9 in the exhaust pipe 6 to generate a pressure difference before and after the exhaust gas sensor 13. That is, instead of the intake communication passage 31 of the third embodiment, one end of one exhaust downstream communication passage 41 (gas exchange promoting means) is connected to the exhaust gas sensor 13, and the exhaust downstream communication passage 41 is connected to the exhaust pipe 6. The other end is connected to the downstream side of the catalyst 9.

  Then, compared with the branch 3 of the exhaust manifold 1 to which the exhaust communication path 11 is connected, the exhaust pressure is increased on the upstream side of the catalyst 9 to which the exhaust downstream communication path 41 is connected due to the throttle effect of the catalyst 9 and the like. Therefore, a pressure difference is generated before and after the exhaust gas sensor 13. Therefore, the exhaust gas in the exhaust communication passage 11 flows through the exhaust gas sensor 13 to the low-pressure side exhaust downstream communication passage 41, and as a result, the exhaust gas of each cylinder is smoothly transferred to the exhaust gas sensor 13 through the exhaust communication passage 11. Therefore, gas exchange of the exhaust gas in the exhaust communication passage 11 can be promoted.

  By the way, at the time of cold start, a phenomenon occurs in which unburned gas due to an increase in fuel is exhausted by bypassing the catalyst 9 via the exhaust downstream communication passage 41. Therefore, as shown by a broken line in FIG. 6, the exhaust downstream communication passage 41 is provided with an opening / closing valve 42 similar to that of the third embodiment, and the opening degree of the opening / closing valve 42 is reduced or fully closed at the time of the cold start or the like. The amount of exhaust gas flowing through the exhaust downstream communication passage 41 may be limited to prevent unburned gas from being discharged.

The connection location of the exhaust downstream communication passage 41 is not limited to the downstream side of the catalyst 9, but may be the upstream side of the catalyst 9. In this case, if the exhaust downstream communication passage 41 is connected to the downstream side of the existing throttle part provided in the exhaust pipe 6 or the downstream side of the throttle part newly provided to generate a pressure difference, the catalyst 9 and A similar throttling effect can be obtained and gas exchange can be promoted.
[Fifth Embodiment]
FIG. 7 is a view showing a connection state of the cooling space of the multi-cylinder internal combustion engine of the present embodiment. In this embodiment, for the purpose of promoting gas exchange, a cooling space 51 (gas exchange promoting means) is provided in the exhaust downstream communication passage 41 described in the fourth embodiment. That is, as in the fourth embodiment, the exhaust gas sensor 13 and the downstream side of the catalyst 9 in the exhaust pipe 6 are connected by the exhaust downstream communication passage 41. In addition, in this embodiment, the cooling space 51 is located in the middle of the exhaust lower communication passage 41. Is provided.

  Accordingly, the exhaust gas that has passed through the exhaust gas sensor 13 is introduced into the cooling space 51 through the exhaust downstream communication passage 41 and undergoes a volume change (volume reduction) due to a temperature drop, and an exhaust gas upstream of the cooling space 51 in accordance with this volume change. Exhaust gas in the downstream communication passage 41 is transferred into the cooling space 51, and exhaust gas in the exhaust communication passage 11 is transferred to the exhaust downstream communication passage 41 via the exhaust gas sensor 13, resulting in the fourth not having the cooling space 51. Compared with the embodiment, the gas exchange of the exhaust gas in the exhaust communication passage 11 can be further promoted.

  Here, in order to efficiently promote the gas exchange in the exhaust communication passage 11 by the cooling space 51, almost the entire amount of the exhaust gas in the exhaust communication passage 11 is exhausted downstream from the exhaust space along with the volume change of the exhaust gas in the cooling space 51. It is desirable to transfer to the passage 41 side. For this purpose, the volume of the cooling space 51 or the volume of the exhaust communication passage 11 or the temperature drop in the cooling space 51 is set so that the volume change of the exhaust gas in the cooling space 51 and the volume of the exhaust communication passage 11 are approximately the same. What is necessary is just to set at least 1 or more of rates.

In addition, without providing the independent cooling space 51 in the exhaust downstream communication path 41 as described above, for example, the exhaust downstream communication path 41 itself, or a part of the exhaust downstream communication path 41, for example, a fin or a cooling water distribution path A cooling device may be provided to function as the cooling space 51.
In this embodiment, the cooling space 51 is provided in the exhaust downstream communication passage 41. However, the cooling space 51 can be provided in the intake communication passage 31 described in the third embodiment. Gas exchange can be further promoted with the same effects.

Although the description of the second to fifth embodiments relating to the gas exchange promoting means has been completed above, various embodiments other than these embodiments can be considered and will be sequentially described below.
[Sixth Embodiment]
The present embodiment is different from the first embodiment in which the exhaust communication passage 11 is provided outside the exhaust manifold 1 in that the exhaust communication passage 11 is incorporated. 8 is a front view showing the head side spacer member of the multi-cylinder internal combustion engine of the present embodiment, FIG. 9 is a front view showing the manifold side spacer member, and FIG. 10 is a sectional view showing the assembled state of each spacer member. is there. In the following description, the cylinder head side corresponding to the left side of FIG. 10 is referred to as the head side, and the exhaust manifold side and the manifold side corresponding to the right side of FIG. 10 are referred to. The state which looked at the member from the head side is shown.

  The head-side spacer member 61 and the manifold-side spacer member 62 have a plate shape similar to the upstream flange 2 (shown in FIG. 1) of the exhaust manifold 1, and the head-side spacer member 61 is on the head side, and the manifold-side spacer member is In a state where 62 is arranged on the manifold side, it is interposed between the cylinder head 63 and the upstream flange 2 of the exhaust manifold 1. Both spacer members 61, 62 are fastened together with exhaust manifold mounting bolts 64 using bolt holes 61 a, 62 a penetrating therearound, and are fixed to the cylinder head 63 together with the exhaust manifold 1. Exhaust gas from each exhaust port 10 (shown in FIG. 1) flows to the exhaust manifold 1 side through four port communication holes 65 penetrating the members 61 and 62.

  A circular sensor fixing base 12 is welded to the manifold side surface of the manifold side spacer member 62 at a position slightly above the port communication hole 65 between the # 2 cylinder and the # 3 cylinder. A screw hole 67 for fixing the exhaust gas sensor is formed, and an insertion hole 68 is formed in the manifold side spacer member 62 so as to correspond to the screw hole 67. One end of a bending path 69 opens on the surface of the manifold side of the head side spacer member 61 corresponding to the insertion hole 68 of the manifold side spacer member 62, and the bending path 69 is bent upward at a substantially right angle. The other end of the path 69 opens to the upper edge of the head side spacer member 61 through the screw hole 70.

  The exhaust gas sensor 13 is screwed and fixed to the screw hole 67 of the sensor fixing base 12, the detection part 13 a of the exhaust gas sensor 13 is located in the insertion hole 68 and the bending path 69, and the tip of the detection part 13 a is the bending path. The horizontal part in 69 has reached almost the innermost part. On the other hand, one end of the intake communication passage 31 of the third embodiment or the exhaust downstream communication passage 41 of the fourth embodiment is connected to the screw hole 70 of the head side spacer member 61, and these communication passages 31, 41 are connected. And communicates with the intake manifold 32 of the internal combustion engine and the downstream side of the catalyst 9 of the exhaust pipe 6.

  Four straight grooves 71 that connect the respective port communication holes 65 and the insertion holes 68 are formed on the surface of the manifold side spacer member 62 on the head side. As shown in FIG. In the state where the head side spacer member 61 is overlapped, each groove 71 is closed by the head side spacer member 61 and functions as the exhaust communication path 11 of the first embodiment that communicates each exhaust port 10 and the exhaust gas sensor 13.

  In this embodiment as well as the first embodiment, the distance A1 from the exhaust port 10 to the exhaust gas sensor 13 is reduced to the minimum necessary, and the distance A2 from the exhaust port 10 to the upstream inlet of the catalyst 9 (FIG. 1), the exhaust air exhaust gas discharged from the exhaust port 10 is minimized in transport delay until the exhaust gas reaches the exhaust gas sensor 13, and the exhaust air / fuel ratio is reduced with extremely good responsiveness. Since the exhaust gas of each cylinder can be detected by the common exhaust gas sensor 13, the manufacturing cost of the internal combustion engine can be reduced.

  In addition, since the exhaust communication path 11 is formed in the spacer members 61 and 62 and the spacer members 61 and 62 are interposed between the cylinder head 63 and the upstream flange 2 of the exhaust manifold 1, Heat dissipation of the exhaust gas flowing through the communication path 11 is suppressed. Therefore, the exhaust gas can be supplied to the exhaust gas sensor 13 while maintaining a high temperature, and another advantage that inactivation prevention and early activation of the exhaust gas sensor 13 can be realized.

  The configuration for suppressing the heat radiation of the exhaust gas in the exhaust communication path 11 is not limited to the above. For example, in the first embodiment in which the exhaust communication path 11 is provided outside the exhaust manifold 1, Even if 11 is configured as a double pipe or the exhaust communication passage 11 is covered with a heat insulating material, the heat radiation of the exhaust gas is suppressed, and the same effect as the present embodiment can be obtained. Further, instead of suppressing the heat dissipation of the exhaust gas, the exhaust gas sensor 13 may be actively heated by a heater or the like to prevent inactivation and activate early.

On the other hand, the head side spacer member 61 and the manifold side spacer member 62 are not limited to the above configuration and can be variously changed.
In the sixth embodiment, a curved path is formed in the head side spacer member 61 and the exhaust gas sensor 13 is connected to the intake communication path 31 and the exhaust downstream communication path 41. However, as in the first embodiment, the intake communication path 31 and the exhaust gas are connected. The downstream communication path 41 may be omitted. In this case, promotion of gas exchange due to the pressure difference cannot be expected, but the effect of suppressing the heat release of the exhaust gas can be obtained in the same manner as in the sixth embodiment.

  In the sixth embodiment, as shown in FIG. 10, the tip of the detection part 13a of the exhaust gas sensor 13 is positioned at the most innermost part of the horizontal part in the curved path 69. For example, as shown in FIG. The plate thickness of 61 may be increased so that the tip of the detection portion 13a of the exhaust gas sensor 13 remains in the middle of the horizontal portion in the curved path 69. In this case, since the flow state of the exhaust gas with respect to the detection unit 13a of the exhaust gas sensor 13 is different from that in FIG. 10, the arrangement of the exhaust gas sensor 13 may be selected in consideration of the characteristics of the exhaust gas sensor 13 and the like.

  In the sixth embodiment, the exhaust gas sensor 13 and the intake communication passage 31 or the exhaust downstream communication passage 41 are communicated with each other via the bent path 69 formed in the head side spacer member 61. A groove 72 may be formed in the spacer member 62 to replace the bending path 69. Specifically, as shown in FIG. 12, a single groove 72 extending upward from the detection portion 13 a of the exhaust gas sensor 13 is formed in the manifold side spacer member 62, and the groove 72 is closed by the head side spacer member 61. 73 is formed, and the upper portion of the passage 73 may be connected to the intake communication passage 31 or the exhaust downstream communication passage 41. Since the machining of the groove 72 for the manifold side spacer member 62 is much easier than the machining for forming the bent path 69, the manufacturing cost can be reduced, and the thickness of the head side spacer member 61 can be reduced by eliminating the bent path 69. As a result, the advantage of contributing to downsizing of the internal combustion engine can be obtained.

  In the sixth embodiment, the head side spacer member 61 and the manifold side spacer member 62 are manufactured as independent members separate from the cylinder head 63 and the exhaust manifold 1, and the exhaust communication passage 11 and the exhaust gas are provided in these spacer members 61 and 62. Although the sensor 13 is provided, either one or both of the spacer members 61 and 62 may be integrated with the cylinder head 63 or the exhaust manifold 1. FIG. 13 shows an example in which the head side spacer member 61 is integrated with the cylinder head 63, and the manifold side spacer member 62 is integrated with the exhaust manifold 1. A groove 71 is formed in the upstream flange 2 of the exhaust manifold 1. While the exhaust gas sensor 13 is fixed, a bending path 69 is formed in the cylinder head 63 so as to communicate with the detection portion 13a of the exhaust gas sensor 13. If comprised in this way, an internal combustion engine can be reduced in size only by the thickness of both the spacer members 61 and 62. FIG.

By the way, when the amount of gas exchange in each exhaust communication passage 11 in the exhaust gas sensor 13 is uneven, problems such as the influence of the air-fuel ratio of the specific cylinder becoming stronger or weaker with respect to the sensor output are generated, and accurate exhaust The determination of the air / fuel ratio cannot be expected. Accordingly, seventh and eighth embodiments in which measures for equalizing the exchange of exhaust gas in each exhaust communication passage 11 are implemented will be described below.
[Seventh Embodiment]
FIG. 14 is a front view showing a manifold side spacer member of the multi-cylinder internal combustion engine of the present embodiment. In the present embodiment, gas exchange is equalized by making the volumes of the exhaust communication passages 11 described in the sixth embodiment substantially the same, and other configurations are the same as those in the sixth embodiment. Explain the point with emphasis.

  Four grooves 81 and 82 are formed on the head side surface of the manifold side spacer member 62 as in the sixth embodiment. In this embodiment, the grooves of the # 1 and # 4 cylinders separated from the exhaust gas sensor 13 are formed. Compared to 81, the grooves 82 of the # 2 and # 3 cylinders close to the exhaust gas sensor 13 are formed wider with the same depth, and have a larger cross-sectional area. With this setting, the volume from the port communication hole 65 to the insertion hole 68 of all the exhaust communication paths 11 is substantially equal.

As described above, since the volumes of the exhaust communication passages 11 are substantially equal, the pressure pulsation when the exhaust gas circulates in the interior is equally affected to perform gas exchange evenly and accurately reflect the air-fuel ratio of each cylinder. It is possible to realize an accurate exhaust air / fuel ratio determination.
As a method for adjusting the cross-sectional area of each exhaust communication passage 11, the depth may be changed instead of the width of the grooves 81 and 82, or both the width and the depth may be different.

Here, depending on the length of each exhaust communication passage 11, resonance of pressure pulsation may occur inside, and the resonance of pressure pulsation fluctuates the exhaust gas flow rate and fluctuates the output of the exhaust gas sensor 13. Therefore, it is desirable to set the length of each exhaust communication passage 11 so as not to cause pressure pulsation resonance in the normal rotation region of the engine.
[Eighth Embodiment]
FIG. 15 is a perspective view showing an arrangement state of each exhaust communication path with respect to the intake communication path or the exhaust downstream communication path of the multi-cylinder internal combustion engine of the present embodiment. In the present embodiment, the exhaust communication passages 11 are arranged at equal intervals with respect to the intake communication passage 31 and the exhaust downstream communication passage 41, and the other configurations are the same as those of the first embodiment. I will explain it.

  One end of four exhaust communication passages 11 is connected to the sensor fixed base 12 to which the exhaust gas sensor 13 is attached, and each exhaust communication passage 11 is centered on the sensor fixed base 12 at regular intervals every 90 °. Although not shown, the other end of each exhaust communication passage 11 is connected to the branch 3 of each cylinder of the exhaust manifold 1. One end of the above-described intake communication passage 31 of the third embodiment or the exhaust downstream communication passage 41 of the fourth embodiment is connected to the lower surface of the sensor fixing base 12, and the other ends of these communication passages 31 and 41 are connected to the internal combustion engine. The engine is connected to the intake manifold 32 of the engine and the downstream side of the catalyst 9 of the exhaust pipe 6.

  With the arrangement of the communication passages 11, 31, and 41, the exhaust communication passages 11 are positioned at substantially equal intervals with respect to the intake communication passage 31 and the exhaust downstream communication passage 41. Exhaust gas flows through the exhaust gas sensor 13 into the intake communication passage 31 and the exhaust downstream communication passage 41 under substantially the same conditions. As a result, the entire circumference of the detection unit 13a of the exhaust gas sensor 13 is effectively used for air-fuel ratio detection, so that the responsiveness is improved and the influence of the air-fuel ratio of the specific cylinder is prevented from becoming strong or weak. Accurate exhaust air-fuel ratio determination that uniformly reflects the air-fuel ratio of each cylinder can be realized.

By the way, when the intake communication passage 31 is connected to the exhaust gas sensor 13 as in the third embodiment, the amount of exhaust gas flowing through the exhaust gas sensor 13 increases with an increase in the pressure ratio between the exhaust pressure and the intake pressure, and the pressure ratio is increased. When the critical ratio is reached and a critical state is reached, the increase in exhaust gas flow rate is limited. Various advantages can be obtained by generating a critical state at the outlet or inlet of the exhaust gas sensor 13 using this phenomenon. Each case will be described below as ninth and tenth embodiments.
[Ninth Embodiment]
In the present embodiment, the cross-sectional areas of the exhaust communication passages 11 and the intake communication passages 31 are set so that a critical state occurs on the outlet side of the exhaust gas sensor 13 for the purpose of reducing the pressure-dependent influence of the exhaust gas sensor 13. Has been. That is, the total sum of the effective joint areas of the exhaust communication passages 11 with respect to the exhaust gas sensor 13 is set larger than the effective joint area of the intake communication passages 31 with respect to the exhaust gas sensor 13.

  FIG. 16 is an explanatory diagram showing the pressure distribution before and after the exhaust gas sensor 13 when the exhaust gas pressure reaches a critical state in the multi-cylinder internal combustion engine of the present embodiment. By setting the cross-sectional area as described above, if the pressure ratio between the exhaust pressure and the intake pressure increases during the exhaust gas flow, the outlet side of the exhaust gas sensor 13 (intake manifold) is earlier than the inlet side of the exhaust gas sensor 13 (exhaust communication passage 11 side). The passage 31 side) reaches a critical state, and the increase in the exhaust gas flow rate is restricted at this point.

The exhaust gas pressure at this time is the exhaust pressure on the upstream side and the intake pressure on the downstream side with the outlet side of the exhaust gas sensor 13 as a boundary, and the exhaust gas sensor 13 has an exhaust pressure closer to the atmospheric pressure than the intake pressure. Works. In general, the exhaust gas sensor 13 has the property of varying the detection characteristics depending on the exhaust gas pressure, but the exhaust pressure close to the atmospheric pressure acts to reduce the pressure-dependent effect, thus improving the determination accuracy of the exhaust air / fuel ratio. Can be made.
[Tenth embodiment]
In the present embodiment, when it is not necessary to implement measures against the pressure dependency of the exhaust gas sensor 13 of the ninth embodiment, for example, when the influence of the pressure dependency is small or when the gas pressure correction is performed for the pressure dependency. It is assumed that, for the purpose of equalizing the amount of exhaust gas flowing into the exhaust gas sensor 13 from each exhaust communication passage 11, so that a critical state occurs on the inlet side of the exhaust gas sensor 13 contrary to the ninth embodiment, The cross-sectional areas of the exhaust communication passages 11 and the intake communication passages 31 are set. That is, the sum of the effective joint areas of the exhaust communication passages 11 is set smaller than the effective joint area of the intake communication passages 31 to the exhaust gas sensor 13. In the present embodiment, the effective joint areas of the exhaust communication passages 11 are set to be equal to each other.

  FIG. 17 is an explanatory diagram showing the pressure distribution before and after the exhaust gas sensor 13 when the exhaust gas pressure reaches a critical state in the multi-cylinder internal combustion engine of the present embodiment. By setting the cross-sectional area as described above, if the pressure ratio between the exhaust pressure and the intake pressure increases during the flow of the exhaust gas, the inlet side (exhaust system) of the exhaust gas sensor 13 is earlier than the outlet side of the exhaust gas sensor 13 (the intake communication passage 31 side). The passage 11 side) reaches a critical state, and the increase in the exhaust gas flow rate is restricted at this point.

In this way, the inlet of the exhaust gas sensor 13 becomes a critical state, and the joint effective cross-sectional area of each exhaust communication passage 11 is equal, so that the amount of exhaust gas flowing into the exhaust gas sensor 13 from each exhaust communication passage 11 becomes substantially equal, Accurate exhaust air-fuel ratio determination that uniformly reflects the air-fuel ratio of the cylinder can be realized.
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above-described embodiment, the invention is embodied as an in-line four-cylinder internal combustion engine. However, if the number of cylinders is large, the number of cylinders and the cylinder arrangement are not limited to this and can be arbitrarily changed.

Moreover, it is not limited to the case where the structure of each said embodiment is implemented separately, It can implement combining the structure of each embodiment arbitrarily, for example, is the exhaust communication path 11 of exhaust gas flow line L1. You may combine the structure of 2nd Embodiment which has arrange | positioned the inflow part 21 at an acute angle, and the structure of 5th Embodiment which provided the cooling space 51 in the exhaust downstream communication path 41. FIG.
Further, the intake communication passage 31 may be connected not to the intake manifold 32 but to the EGR downstream passage.

Further, when the pressure difference is such that gas exchange cannot be promoted (for example, intake pipe negative pressure increase, upstream exhaust pressure decrease, downstream exhaust pressure increase), the air-fuel ratio determination may be stopped.
Further, it is preferable that the relationship between the vent provided in the protective cover of the exhaust gas sensor 13 and the communication port of the exhaust communication passage 11 flowing into the exhaust gas sensor 13 is made uniform for each cylinder. When the flow rate of the exhaust gas (inspection gas) flowing into the exhaust gas sensor 13 is high, the amount of inspection gas that reaches the detection unit 13a of the exhaust gas sensor 13 depending on whether there are a large number or a small number of vent holes on the projection surface of the passage port. However, there is a problem that the air-fuel ratio is likely to be affected by the air-fuel ratio variation between the cylinders, but this problem can be reduced.

  Further, the cross-sectional areas of the exhaust communication path 11, the intake communication path 31 and the exhaust downstream communication path 41 do not have to be uniform in each path as shown in the embodiment, and the portion where the cross-sectional area is the smallest is one of the paths. You may make it become only a part. Since exhaust gas passes through each passage, the cross-sectional area of the passage changes due to adhesion of debogit, for example, when the effective cross-sectional area of each exhaust communication passage 11 is not uniform among the cylinders, the cylinder is used for air-fuel ratio determination. Although there is a problem that there is a variation in the gap, debogit does not adhere uniformly in the passage, so reducing the probability that deposits etc. adhere to the minimum cross-sectional area by making the minimum cross-sectional area part. Can do.

As a result, the probability that the effective cross-sectional area of each exhaust passage is non-uniform among the easy passages can be reduced, and deterioration in determination accuracy due to variation between cylinders in air-fuel ratio detection can be suppressed.
Further, the exhaust gas introduced through each exhaust communication passage may be mixed in the space of the exhaust gas sensor 13, and the mixed exhaust gas may be determined by the exhaust gas sensor 13. May be determined individually.

1 is an overall configuration diagram showing a multi-cylinder internal combustion engine of a first embodiment. It is a characteristic view showing the relationship between the modulation cycle of the air-fuel ratio, the CPO purification efficiency, and the window width. It is sectional drawing which shows the connection state of the exhaust communication path with respect to the exhaust manifold of the multicylinder internal combustion engine of 2nd Embodiment. It is sectional drawing which similarly shows another example of the connection state of an exhaust communication path. It is a figure which shows the connection state of the intake communication path of the multicylinder internal combustion engine of 3rd Embodiment. It is a figure which shows the connection state of the exhaust downstream communication path of the multicylinder internal combustion engine of 4th Embodiment. It is a figure which shows the connection state of the cooling space of the multicylinder internal combustion engine of 5th Embodiment. It is a front view which shows the head side spacer member of the multicylinder internal combustion engine of 6th Embodiment. It is a front view which similarly shows a manifold side spacer member. It is sectional drawing which similarly shows the assembly | attachment state of each spacer member. It is sectional drawing which shows another example which increased the plate | board thickness of the head side spacer member. It is sectional drawing which shows another example which formed the groove | channel in the manifold side spacer member instead of the bending path. It is sectional drawing which shows another example which abbreviate | omitted the spacer member. It is a front view which shows the manifold side spacer member of the multicylinder internal combustion engine of 7th Embodiment. It is a perspective view which shows the arrangement | positioning state of each exhaust communication path with respect to the intake communication path of the multicylinder internal combustion engine of 8th Embodiment, or an exhaust downstream communication path. It is explanatory drawing which shows the pressure distribution before and behind an exhaust gas sensor when exhaust gas pressure reaches a critical state in the multicylinder internal combustion engine of 9th Embodiment. It is explanatory drawing which shows the pressure distribution before and behind an exhaust gas sensor when exhaust gas pressure reaches a critical state in the multicylinder internal combustion engine of 10th Embodiment.

Explanation of symbols

1 Exhaust manifold (exhaust passage)
3 Branch (exhaust port side exhaust passage)
4, 8 Exhaust passage junction 6 Exhaust pipe (exhaust passage)
9 Catalyst 10 Exhaust port 11 Exhaust communication path 13 Exhaust gas sensor 21 Inflow part (gas exchange promoting means)
31 Intake communication passage (gas exchange promotion means)
33, 42 Open / close valve 41 Exhaust downstream communication passage (gas exchange promoting means)
51 Cooling space (gas exchange promotion means)

Claims (9)

In a multi-cylinder internal combustion engine having a plurality of cylinders,
A catalyst for purifying exhaust gas provided in an exhaust passage extending from the exhaust port of each cylinder;
An exhaust communication passage that is built in a flange joint between the cylinder head of the internal combustion engine and the exhaust passage, and communicates at least two of the exhaust passages;
An exhaust gas sensor provided in the exhaust communication path,
A multi-cylinder internal combustion engine characterized in that the distance from the exhaust port to the exhaust gas sensor is shorter than the distance from the exhaust port to the upstream inlet of the catalyst. The exhaust communication passage is formed as a groove on at least one of the flange surfaces of the cylinder head side and the exhaust passage side of the internal combustion engine, and is closed when the flange is joined to function as a passage. The multi-cylinder internal combustion engine according to claim 1. In a multi-cylinder internal combustion engine having a plurality of cylinders,
A catalyst for purifying exhaust gas provided in an exhaust passage extending from the exhaust port of each cylinder;
An exhaust communication passage communicating at least two or more of the exhaust passages;
An exhaust gas sensor provided in the exhaust communication path;
An exhaust communication passage that communicates the exhaust gas sensor and the intake system of the internal combustion engine and promotes gas exchange in the exhaust communication passage by a pressure difference between the exhaust pressure and the intake pressure;
A multi-cylinder internal combustion engine, wherein a sum of effective joint areas of the exhaust communication passages with respect to the exhaust gas sensor is set larger than a joint effective sectional area of the intake communication passages with respect to the exhaust gas sensor. In a multi-cylinder internal combustion engine having a plurality of cylinders,
A catalyst for purifying exhaust gas provided in an exhaust passage extending from the exhaust port of each cylinder;
An exhaust communication passage communicating at least two or more of the exhaust passages;
An exhaust gas sensor provided in the exhaust communication path;
And communicating the intake system of the exhaust gas sensor and the internal combustion engine, and an intake communication passage that promotes gas exchange in the exhaust communication passages due to the pressure difference between the exhaust pressure and the intake pressure,
The sum of the effective joint areas of the exhaust communication passages to the exhaust gas sensor is set smaller than the effective joint area of the intake communication passages to the exhaust gas sensor, and the connection of each exhaust communication passage to the exhaust gas sensor. A multi-cylinder internal combustion engine characterized in that effective cross-sectional areas are set substantially equally to each other. Downstream of the upper Sharing, ABS gas sensor, cooling space to promote gas exchange in the exhaust communication passage is formed by a volume change caused by cooling of exhaust gases,
At least one of the volume of the cooling space, the volume of the exhaust communication path, and the temperature decrease rate in the cooling space is set so that the volume change of the exhaust gas in the cooling space is approximately the same as the volume of the exhaust communication path. The multi-cylinder internal combustion engine according to claim 3 or 4, wherein the multi-cylinder internal combustion engine is set. 6. The multi-cylinder internal combustion engine according to claim 3, wherein each of the exhaust communication passages is disposed at substantially equal intervals at predetermined angles on a substantially horizontal plane with respect to the intake communication passage. The multi-cylinder internal combustion engine according to any one of claims 3 to 6, wherein the intake communication passage includes an open / close valve capable of adjusting an amount of exhaust gas flowing through the intake communication passage. In a multi-cylinder internal combustion engine having a plurality of cylinders,
A catalyst for purifying exhaust gas provided in an exhaust passage extending from the exhaust port of each cylinder;
An exhaust communication passage communicating at least two or more of the exhaust passages;
An exhaust gas sensor provided in the exhaust communication path;
Communicates the downstream side of the catalyst in the exhaust system of the exhaust gas sensor and the internal combustion engine, the exhaust downstream communication passage to promote gas exchange in the exhaust communication passages due to the pressure difference between the upstream side and the downstream side of the exhaust system When,
An open / close valve provided in the exhaust downstream communication passage, and capable of adjusting an amount of exhaust gas flowing through the exhaust downstream communication passage;
A multi-cylinder internal combustion engine comprising: 9. The multi-cylinder internal combustion engine according to claim 8, wherein the exhaust communication passages are arranged at substantially equal intervals at predetermined angles on a substantially horizontal plane with respect to the exhaust downstream communication passage.

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